Indicating and recording equipment



NOV. 10, 1953 L, w, ZABEL ET AL 2,659,048

INDICATING AND RECORDING EQUIPMENT Filed Feb. I5. 1948 5 Sheets-Sheet l Nov. 10, 1953 1 w. ZABEI. ETAL INDICATING AND RECORDING EQUIPMENT 5 Sheets-Sheet 2 Filed Feb. 5, 1948 Nov., '10, 1953 L. w. ZABEL ET AL 2,659,048

INDICATING AND RECORDING EQUIPMENT Filed Feb. 5, 194e 5 sheets-sheet s Adm/"411m l ggg: 5

Nov. 10, 1953 1 w. zABEL ETAL 2,659,048

INDICATING AND RECORDING EQUIPMENT Filed Feb. 5, 1948 5 Sheets-Sheet 4 /IW i "F Nov. 10, 1953 L. W. ZABEL ET AL INDICATING AND RECORDING EQUIPMENT Filed Feb. 5, 1948 5 Sheets-Sheet 5 Patented Nov. 10, 1953 65ans INDICATING AND RECORDING EQUIPMENT Lowell W. Zabel and Robert W. Schmidt, Neenah, and RalphH. Caston, Appleton, Wis.,'assgnors to Paper Patents Company, Neenah, Wis., a. corporation of Wisconsin Application February 3, 1948, Serial No. 5,986

The present invention relates particularly to apparatus for measuring the moisture content of a web of paper, either while such web is being manufactured on a papermaking machine, or as a subsequent operation.

In the manufacture and processing of various types and grades of paper, the quality of the paper and the efficiency of the operation are both closely related to the moisture content of the paper web. To obtain the best possi-ble results, it is very desirable that the machine operator be informed at all times regarding the moisture content of the web being manufactured or processed, and it is also desirable that the operator lbe able to ascertain the moisture content at various positions across the web. As a result, various devices and instruments have been developed for determining the moisture content of paper Webs, but the arrangements heretofore available and used in the papermaking art have been of a somewhat makeshift character and have been generally unsatisfactory. Of particular importance in this connection, the results obtainable from the use of the known devices have either been very diiicult of interpretation or have been unreliable.

There is, therefore, an existing need in the papermaking art for apparatus which is capa-ble vof accurately measuring and indicating the moisture content of a paper web as it is manufactured on a papermaking machine, or as it is passed through a converting or other processing machine, and the provision of improved apparatus for this purpose constitutes the principal object of the'present invention.

It is also an object of the invention to provide a simple, efficient means for measuring the average moisture content across the Width of a moving web of paper, and for indicating and recording this measurement, al1 as a continuous operation. Further objects of the invention include the provision of means for determining, continuously, the instantaneous variation in moisture content of a paper web across the width of such web and for making available a continuous indication of this variation during the operation of the papermaking machine.

Other and more detailed objects of the invention include the provision of improved indicating and recording equipment, particularly adapted for use in connection with moisture indicating systems in accordance with the principal object of the invention, and also the provision of a novel scanning or sensing roll, especially useful in connection with the indicating and recording 9 Claims. (Cl. 324-65) equipment of the present invention. Various features of the invention and certain illustrative embodiments thereof will be made more apparent in the following description and the accompanying drawings, wherein,

Fig. 1 is a diagrammatic view of a Fourdrinier papermaking machine equipped with moisture indicating and recording apparatus in accordance with the invention:

Fig. 2 is a front elevational view showing a scanning or sensing roll in accordance with the invention, applied to a papermaking machine of the general type illustrated in Fig. l;

Fig. 3 is a side elevational view of the mechanism illustrated in Fig. 2;

Fig. 4 is a fragmentary, perspective View illustrating the features of the support and lifting ures 2 and 3;

Fig. 5 is a sectional view showing certain of the features of the scanning roll illustrated in Figures 2 4 of the drawings;

Fig. 5a is a fragmentary, perspective View f a modified scanning roll of the general type illustrated in Figure 5;

Fig. 6 is a circuit diagram of a moisture content indicating system embodying some of the features of the present invention;

Fig. '7 is a graphy illustrating the manner in which one of the resistances shown in the circuit of Figure 6 is varied in order to obtain a linear response characteristic in the indicating instrument;

Fig. 8 is a diagrammatic illustration of a practical embodiment of the circuit illustrated in Figure 6;

Fig. 9 is a circuit diagram of an electronic circuit which is particularly suited for use in a moisture indicating and recording apparatus in accordance with the invention;

Fig. l0 is a graph illustrating the electrical characteristics of the electronic tube circuit illustrated in Figure 9;

Fig. l1 is a diagrammatic illustration, generally similar to Figure 8, showing the features of a, moisture indicating and recording system employing the electronic circuit of Figure 9;

Figure l2 is a fragmentary perspective view of another modified form of scanning roll; and

Figure 12a is a fragmentary perspective view of still another modified form of scanning roll.

It is a known physical fact that the variation of the electrical resistance of a web (or sheet) of paper constitutes an accurate measure of the variation in moisture content of that web. For

vention provides an approximately Alinear indica,

tion in response to variationin the-moisture. content of the web with which it is used. This obviates many of the difiiculties experienced with :the non-linear indicating means of the prior art and greatly facilitates the interpretation of the. readings obtained. The apparatus of the invention includes a, novel scanning or sensing means where..- by it becomes possible* to .determinelbothinstantaneous and average variations invmoisture. content acrossthe width o f the-Web. The feature of the invention makes possible-the, practical utilization of cathode ray. oscilloscopes..forobtaining a continuous, instantaneous indicationof moisture content variation across the Widthv of the Web.A

In Figure l of the drawingsithereis.y illustrated, in generally diagrammatic form, a Fourdrinier papermaking machine of conventionaltype.v This machine includes a head boxl 2|, or'other means, for delivering the stockto the wire, aFourdrinier wire 23 which is supported at its ends bythe usual breast and couch rolls2 5 and 21, andwhch may be. supported intermediate its length by suitable table rolls, three of which are illustrated at 29. Suction boxes and like means for facilitating the drainage of the web are indicatedat 3|, and a dandy roll is shown-at 33. The formedpaper web 35.-is removed from the wire 23 A,and is conducted through press rolls, two pairs of which are indicated at 3l and .38 by. means of suitable felts 34 and 36. After leaving the press ro11s,.the `web 35 is conducted through the .one or more. drier sections, an illustrative unitfof which is shown at 4|.

The drier sectionAl is of conventional :design and includes a series of heatedv drier rolls 4'3, and a pair of felts 45 WhichI are arranged to.press the paper web 35 into contact with the-A drier rolls. Each of the felts 45 is supported bysuitable guide and tightening ro1ls41, and the apparatus may include one ror more ponydriers, as-.illustrated at 49g As previously noted; aplurality---of drier sections, similar to the drier section 4I, may be used in accordance with conventional paper manufacturing practice. In the illustrated apparatus, the dried web 35, after leaving the drier 4|, is conducted over suitable guide rolls 5l and 52 to a calender stack, illustrated at 53; The calender stack 53 is of conventional design and after passage therethrough, the now dried and calendered web 35 is conducted-to suitable reeling mechanism, not shown.

It will be understood that the disclosure in the drawings of a multiple cylinder type` drier is merely illustrative. Should the machine. be manufacturing athin, creped, cellulosicvsheet, a

Yankee type drier would -be used; and for thepurposes of this invention, the particular drier used is not important.

Moisture indicating andv recordingapparatus in accordance with the present invention .is-embodied in the papermakingmachine illustratediin Figure l. This apparatus includes a scanning or sensing roll, illustrated diagrammatically at 55, and a moisture recording and indicating instru ment, illustrated diagrammatically at 5l.

The features of the scanning or sensing roll 55 are shown particularly in Figures 2 through 5. The function-of this roll fiato-provide a scanning electrodeorcontact which,v in effect, moves across the web of paper as it is manufactured on the machine, thereby providing means for continuouslyldetermining the electrical resistance and the moisture' content across the moving web. The scanning roll 55. includes a central core 59 of steelshaftingor other suitable rigid metal. An insulating ringGI `is disposed at either end of the centrall shaft 59, and these rings 6I serve to support a. metallic tube G3, which in turn serves as the support for an insulating sleeve 65 which provides the roll surface.

The insulating sleeve 65 should be manufactufee.. of. eterniy having very. ugh.- emulation resistancei such as rubber, a.. reinforced -phenol-- folmalhyd T esl z0.f' knQWn typen 0r' am", oh. suitable material, and in the illustrated embodif ment of the invention, a,strip 6i yof .A conducting metal, such aszbrass or copper, which .is bentin a generally spiral form, is attachedto, and .recessed inl this sleeve., as illustrated, The spiral -metallic strip 61- makes one complete.. turn about'the. surf face of the scanning orsensing rol155 and it is anchored Ain place and, electricallyf connected to the inner xsleeve .63 by*A means ofl ay plurality-4 of spaced Screws @Studs-:63. as fshewna. Desirably. the y surface of theinsulatingsleeve,v 65. andthe spiral electrode 6l are ,grcurd;.smocthand.1ush with each othertoprovidea properyrll surface. In one practical embodiment of the. invention, the scanning rollf55 had an overalllength,ofafbout 46 inches, and a maximum external .diameter .of 51/2- inches. The insulating .sleeve ,65 in ,this roll;I

had a width of 28I inches and a uniform thickness` :trated in Figure. 12, the. electrodestrip. canbe divided into sections 61a, each ofwnich is connectedto a collector-ring4 or tofafcommutator segment 61h at `one-endrof the-roll.v This. construction makes it possible. to obtainaseresof sensings Ifroma particularsection or.sections of thefweb. Alternatively, as illustrated in Figure 12a.,.al series of short 360" spiral sections 61e can be-.used to.A advantage incertain instances.

A. further modified construction ofthe scanningor.sensing roll is shown at 55a. inthe fragmentary view- Figure 5a. In thisconstruction, theconducting `electrode. .in the surface ot the roll is provided :by a solid, generally-radially .extending n 1l, of `brassor bronze. or other-.conducting material, which is-welded-or otherwise affixed to the conductingsleeve portionl .63 of. the roll 'in a manner similar to the .ight of an auger conveyor. The electrode 'H isvthusin the form of. an up-ended strip andv is shaped so as to -provide one spiral turn around the-roll surface.T The insulating sleeve or roll ycover Il 5 is applied` tof-the tubular Vportion B3 with the conducting stripv H in place,v and as in the .previousdescribedponstruction, this portion of thevroll should. be manufactured of a material having high insulation value. After the roll covering operation, the surface of the roll should be turned down and ground to provide the proper smooth surface.

During use, the scanning or sensing roll is supported parallel to, and adjacent one of the driers or some other roll in the paper machine, and the web of paper which is to be subjected to a moisture determination test is passed through the nip formed between the scanning roll and this cooperating roll. Electrical contact to the spiral electrode is conveniently made by a-brush-contact 12 which contacts the sleeve portion 83 of the scanning roll, as illustrated in Fig. 4. In the paper machine illustrated in the drawings, the scanning roll 55 is supported directly above one of -the guide rolls 52, preceding the calender 53. It will be understood that the scanning roll 55 can -be disposed in cooperative relation with one of the drying cylinders 43, with one of the metallic rolls in the calender stack 53, or in any other location where moisture content determination might be desired. The essential feature is merely that the strip of paper to be tested shall be passed through a nip provided by the scanning or sensing roll and a cooperating roll which has a conductive surface.

To obtain fully reliable, reproducible results, it has been found necessary to maintain moderate pressure along the line of engagement of the scanning roll and the roll which cooperates therewith to provide a sensing region for the paper web. Generally, a linear pressure at the nip of these rolls of the order of about ve pounds per linear inch is satisfactory. Also, in order to permit convenient threading of the machine, it is desirable that the scanning roll shall be movable out of engagement with its cooperating support or drier roll.

In the illustrated apparatus, the support means for the scanning roll 55 includes a pair of support members 13, which have the general outline illustrated in Figures 3 and 4. The support arms 13 are manufactured of insulating material and each is provided with a bearing support 15 for receiving one end of the scanning roll shaft 59. Each of the support members 13 is pivoted to an angle bracket 11 attached to the main frame 19 of the paper machine by a suitable pin 8|. In order to move the support members 13, and with them the scanning or sensing roll 55, there is provided a crank 83 having a shaft 85 which extends transversely of the machine and which is supported upon suitable bearings 81 attached to the machine frame 19. The shaft 85 and the crank 83 are operatively connected to the unpivoted end of each of the roll support members 13 by means of two bell crank levers 89, two short cranks 9|, each of which is keyed to the cross shaft 85, and suitable pins 92 (Fig. 4)

It will be evident that rotation of the main crank 83 and the shaft 85 will raise or lower the unpivoted end of the roll support members 13, and thereby raise and lower the scanning rolls 55 relative to the cooperating support roll 52, as desired. The weight of the scanning roll 52 is usually suicient to produce the desired nip pressure, under normal operating conditions, but if additional pressure is required, this can be accomplished by applying a suitable torque to the cross shaft 85.

In Figure 6 of the drawings, there is illustrated, diagrammatcally, a circuit which can be used in conjunction with a scanning roll as above described for the purpose of measuring the moisture content of a moving web of paper. In this dlagram, a scanning roll 93, which may be similar to the roll 55, is illustrated in contact with a cooperating roll 95, which may be of somewhat larger diameter than the scanning roll and which is of conducting material, at least on the surface thereof. A web of paper 91 is shown as passing between the nip of the rolls 93 and 95. The spiral contact or electrode constituting a part of the scanning or sensing rolls 93 is electrically connected to one end of a battery 99 or other source of` direct current potential; the other end of the'battery 99 is connected through a protective resistance |0| to one side of an indicating and recording instrument |03, which includes a galvancmeter type response element and a motordriven pen mechanism, indicated at |05, which is powered'from a 115 volt, 60 cycle source, as illustrated, and which is controlled by the galvanometer element. This same terminal of the indicating and recording instrument |03 is also connected to one side of a variable resistor |01 having a movable contact |09, which is adapted to be moved in response to movement of the motor-driven mechanism |05 for the recording pen. Th other terminal of the recording instrument |03 is connected to the movable contact |09 of the variable resistor |01 and also to the cooperating roll 95.

The circuit of Figure 6 is operable to measure the resistance of the segment of paper which is between the spiral electrode and the surface of the cooperating roll 95 at any particular instant, and it will be apparent that the segment of paper under test moves progressively across the web surface during each revolution of the scanning or sensing roll 93. Of course, if measurement across the width of the web is not desired, the sensing electrode can comprise a simple narrow disc or roller which contacts the wel; at a fixed point; the circuit will operate with any" type sensing means. Excluding the sensing means, the circuit illustrated in Figure 6 diiers from known resistance-type ohmmeter circuits by the use of a variable shunt resistance, such as resistance |01, which is arranged to be varied in response to movement of the motor driven operating means for the indicating and recording pen of the instrument |03. Ordinary series resistance ohmmeter circuits have a substantially logarithmic response in the mid-portion of the scale, `and in instances where the moisture and resistance variations in the paper are very slight, it is conceivable that it might be possible to measure and record the resistance of such paper continuously by the use of an ordinary series instrument. However, under practical operating conditions, the resistance of a paper web may vary over a ratio of 10,000 to l, or even greater, resistance values from .10 megohm to 1000 megohms being commonly encountered in the operation of the average paper machine. This variation is obviously far beyond the range of even approximate logarithmic response in ordinary series resistance ohmmeters, and as part of this invention, we have provided a resistancetype ohmmeter of novel design which is capable of a substantially logarithmic response for very large variations in resistance. Such an instrument makes possible a substantially linear indication over the entire range of moisture contents consistent with the resistance range given above, and thereby overcomes many of the diniculties of the prior art equipment.

More specically, we have discovered that if a series resistance type ohmmeter is provided with a shunt-resistance across theggavanomiif indicating element. or. thegalvanonLuei'AJr.-I Centr-9.1 forv the. indicating e1ement, whichresistance-.is varied .continuously in responseto; movement; I the instrument indicating. means..A the desired logarithmic response. over a. veryffwide ratio-A of resistance values can beobtaned... thezcr: cuit, as illustratedin Figure.v 6.. Where the. re.-l sistance R1 or wlisa protective resistancin series with the: galvanometer elementi; amhthe variable resistancev Rz or;l |01; is.. connetedein shunt of thegalvanometer elemenisz. itgcan: be shown .that the. instrument.:- I B3 will responds' logr arithmically for Wide.A variations.: in: resistance across the testv electrodes,. whether; providednby the -rolls A9:3 and 95. .or otherwise, if ;thei shunt-re:-4 sistance R2 is.-.vvariedin; accordance withzthefol lowing formula.:

R (RrtRz) (10g. R11-b). 2- mE-logIRgK-'b Where. b and m are constants, depending slope and intercepts of thedesiredfcurve-andthe voltagerange of the measuringinstrumentME is,the battery, vcltage, and; Rxvlis .the resistance of lthergpaper orother material .underitest It.;isd esired thattheindicationof their;- strument shall be directly proportional to the logarithm of the resistance of the paper. Since the instrument actually, measuresya. voltagec, this linear relationship may b e representedgby log- Rx=me+lr where RX is the papenresistance and mand b are constants. If, wefdecideto let `a voltage e1, near the lowerend ot-the. in.- strument scale represent avalue-Rn, at theupper end ofthe desired range of Rx andif--we decide to let a voltage e2 near the upperrangQ-.of -the measuring instrumentcorrespondingn to a value Rxz near the lower end of the desiredrange vof Rx then we may write:

mzlog R11-10g R12 b ei 10g Rs2-e2 10g Ra The graph, Figure 7, shows a curveaderived: by the use of the above formula for a:.particular instrument in which the variationin the resistance R2 was between a low value of. about-.1900; ohms and a high of around 9000 ohms.. Sincefitis in.- convenient to provide a slide Wire resistance which is capable. of varying. in accordance-:with a vcurve such as is illustrated in Figure. '1;' it will be found most convenient to usea tappedfpoint resistor, so arranged that an; approximation o-f theA curve wiil be obtained. Normally, aboutffiO points will be. found suiicient to .produce-a subistantially uniform response in thee instrument. Itwill also be understood that response. characteristics other than logarithmic can beaccom plished by suitable. variation inithe. shunt resistance. So long as theslopesof thedesired'lresponse curve is positive, almost anyA reasonable response characteristic canA be obtained.

It will be apparent that the operation of a circuit as shown in Figure 6 (where thef-shunt resistance R2 is caused to vary. in. accordance with the curve shown in Figure'L: in response to movement of the instrument indicating means) will make possible substantially linear indication of the moisture content of a web. of` paper which is passed between the test electrodes provided by the scanningroll 93"and the support roll"85,1and a complete-system of this character-f is-gshownin,somewhatmore detail in Figure A8. Inrthat:nguregthe-.scanrng or sensing T011 55. previouslyv described, is; illustrated inpcooperative relationwith the support roll 52, and the web of paper; 35. which is to be tested is shown as passing betweenthe nip provided by these rolls. Onefside-of a battery orother source of direct current. p0tential. I I3 is electrically connected to;th.e;-sp ira1 test .electrode 6-1 in the surface of thefsqanmnggroll 55,. this latter connection being madeebyythe-brush 12, although other arrangemeutsfcanfbe'usedf. Theother-sideof the batteryfl tris-.connected to one end of aseries protective-resistor H 5.; Theaotherfend of the .protectiveresistor IIS-connected to one of the inputterminals ||8.` ofA a sensitive, motor control .|.l`l,1.which; constitutesapart of thel indicating and:` recording instrument.- A- multipointe variableA resistor I i9 is connected y across theginpiit terminals H8-and (20.. ofthe-motor ontlloltullitsl Ill-sons to place the variable-,resistcrgllgin shunt-With that unit.

The terminal IML-is,l also connected to the support, rollfkby-suitable means (notv specically shownl'. Themotor-control unit IVI-may be of known type and may include a. sensitive gal- VanQmeter. c. li,tro1,,or a balance unit, and switchingmeans-'which is -operable-upon the application oiazsgnalpotential toxtheinput terminals HB a.n d-|-20\.-to= eifect energizationof a reversible motor;- |21, inga. direction which visdetermined by the direction- .of Athe signal potential. The motor i2! is:arranged- .to operates. balancing potentiometer I23;;.,energized1.vfrom al suitablel potential .source4 |25, and this. pptentiometer is used to provide are potential for. balancing the signal,l potential.; Whenever the-galvanometer unit I'i is thrown out of balance, the motor l2 is operated l and lcontinues to voperate until .the potenticrneteri i2 3., brings the galvanometer into` balance. Since j the motor |21 isalso geared to. a. combination' indicatm:A and,A recording; pen. mechanism l-27 through, a.suitablepinion l29 and a segmental gearqlal ,1 4operation of the .motor to -balance the galyanorneter also. actuates -the. indicating and recording. .means: The indicator and recording. penl coactsfwith a circular record chart 133 which is, driven bya .time clock |35.

In1accomp1ishingthe indicating and recording .function by the ;useof ,a-balancing motor actuatedpotentiometer, the-.apparatus ,is in accord with tpriorpractices.` However, the equipment illustrated Figure-8- also. includes .the multipoint -variable- .l resistor H9 which isconnected acrossfthefinputl .terminals of the galvanometer control unit, and thereversible motor I2!- is mechanicallywconnected to operate the moving contact. |731 ofthis. resistor in unison with the balancing potentiometer 123 and the indicating .Y and, recording pen.|21. The resistance lie, similar tothe resistance` R2 in Figure 6, is designed to effect variation.- .in the shunt resistance in accordancewiththe curve shown in FigureE 7, and as 1aresult the .response of the instrument becomeslinear with response to moisture content. During. actual operation of the apparatus, movement ofgthe sheet Lof paper 35 under test between the-rolls52 and .55.. effects rotation of the scanning* roll.`r 55,.l anda signal potential which is determined by the constants of the circuit and the resistanceof the particular segment of the paperv web which-is between the spiral electrode 61 and the conducting surface of the cooperating roll-y 52 inf'eachparticular instance is transmitted tothesensitive,galvanometer type, motor control unit ||1 of the instrument. By suitable dampening of the motor control and the indicating and recording means, with reference to the speed of rotation of the scanning electrode 61, the instrument can be operated to provide an indication which is a very close approximation of the integrated variation in moisture content across the web under test.

Galvanometer-type motor control units capable of producing full scale response of the indicating means with an applied potential of about 200 millivolts have been used successfully for paper moisture measurements in circuits, as described above, having a battery potential of about 105 volts in the test electrode circuit. The protective resistance I I5 in this circuit had a resistance of 1,000,000 ohms, and the shunt resistance H9 varied from 1430 ohms to 9520 ohms during operation.

The variable shunt resistance unit I 9, as above described, makes possible the practical operation of a shunt-type ohmmeter to provide a substantially logarithmic response for resistance changes which vary in the ratio of 10,000 to 1, or even higher. As above noted, it is also possible by further variation and modification of the shunt resistance characteristics to produce other types of response in the indicating portion of the instrument. The arrangement, however, requires a-substantlal amount of equipment and is subject to certain minor operational difficulties. For these reasons, it vis desirable, in certain instances, to utilize an electronically controlled indicating and recording mechanism in place of the electromechanical structure previously described. In Figure 9, there is illustrated an electronic circuit which can be used for the measurement of resistance and which, when properly designed, is capable of providing a substantially linear current or voltage output in response to logarithmic variation in a resistance connected in the position Rx of the circuit. This response characterist-ic of the circuit pertains for resistance values which mav Vary in a ratio of as much as 100,000 to 1, and the circuit is therefore particularly suitable for use in the determination of the moisture content of paper webs. Preferably. the circuit of Figure 9 utilizes a high amplication factor triode, such as the tube manufactured and sold under the designation 12F-5, although other triodes and triode connected multiple grid tubes can also he used. When the circuit is being used for the determination of moisture content in a paper web, where resistance values from the order of .10 megohm to 1000 megohms, or even higher, are normally encountered and a 12F5 triode is employed. it will be found desirable to use a voltage E of the order of about '75 volts with a resistance in the grid circuit, the resistance Rf; of about 2500 megohms and a cathode resistance Rk of the order of about .500 megohm.

The graph. Figure 10. illustrates the current variation in the several branches of the Figure 9 circuit for various values of resistance in the Exposition. In this graph the resistance Re is plotted on a logarithmic scale whereas the current values are plotted on a linear scale. It will be noted that the cathode current Ik varies as a substantially linear function, inversely with the logarithm of the resistance Rx. The cathode current Ik, and hence the voltage drop across the cathode resistor Rk. is determined by the sum of the plate current Ip and the grid current Ig. For values of Rx below about 10 megohms, the grid current becomes increasingly important as deterl0 minative of the total cathode current, whereas for values of Rx over 10 megohms, the grid current becomes almost negligible. The grid potential is determined by the series relationship of Rx and Rg, the two resistors acting as a voltage divider.

It will be seen that the cathode current Ik approaches a limiting minimum value as Rx is increased, and it can be shown that the rate of approach of Ik to the minimum value is determined, to a large extent, by the ratio of the grid resistance Rg to the resistance Rx. The higher the value of the grid resistance the more slowly the curve approaches the limiting value. Thus, the grid resistor Rg serves the primary function of aiding in straightening the Rx vs. cathode current calibration curve in the range of Rx values above about megohms. The grid resistor for available high mu triodes should have a value within the range of from about 500 to 20,000 megohms, although values as low as 100 megohms can sometimes be used.

The cathode resistor Rx introduces degeneration into the circuit so that normal variations in tube characteristics and supply voltages have little effect on the operation of the circuit. This resistor may have any reasonable value, provided that .it is high compared to the plate resistance of the tube being used. Generally, resistors having values between .land 1.0 megohm are for available high mu triodes.

It will be understood that the relatively high resistance values which this circuit may be called upon to measure necessitate very careful insulating of the test electrodes and all other parts of the circuit, since even with relatively high values of leakage resistance the accuracy of the instrument may be seriously affected. The magnitude of the plate potential is usually not particularly critical and may be of the order of 40 to 100 volts.

Alternating current plate voltage may be used,

since the tube is conductive in only one direction, but greater stability will be encountered t when a direct current plate supply is provided.

Figure 11 is a diagrammatic view illustrating the manner in which an -electronic circuit of the type illustrated in Figure 9 can be used in conjunction with indicating and recording apparatus of various types for measuring and recording the moisture content of a paper web. The circuit illustrated in Figure 11 utilizes a scanning or sensing roll |4| which has a spiral electrode |42, similar to the roll 55, and a paper support roll |43 as the test electrodes (i. e. as the connections to the Rx resistance in the Figure 9 circuit) but it will be'understood that any other suitable type of test electrodes' or sensing means can be used. The paper web under test passes between the nip of the rolls 4| and |43, as indicated at |45, and the segment of paper between the surface of the support roll |43 and the spiral scanning roll contact |42 is connected across the plate and grid of the triode |41, which, as previously noted, may be a 12F5 or other high mu triode. The grid resistance '|49 (Rg) in this arrangement has a value of 2500 megohms and the cathode resistance 5| (Rk) a value lof 500,000 ohms. One side of the cathode resistance 5| is connected directly to the cathode of the triode |41, and the other side of that resistance is connected to one side of the grid resistor |49, to the negative terminal of the plate supply battery |55, and to one terminal of a conventional, galvanometer-type, indicating and recording instrument |57.

rllwo adjustable taps |53 Aa-nd |54 are provided on the cathode resistance and one of these, the tap |53, is connected to the other terminal of the recording instrument |51. This instru ment should be capable of giving full scale de- `flection with a current of about one milliampere or less and a supply :potential of about 40 volts or less. Galvanometer-type indicating and recording instruments Ahaving these operating characteristics are available commercially from both Esterline Angus and the Bristol Company. In operation, a recording pen |59, which is directly connected to a galvanometer and which also serves as an .indicator means, .is arranged to lmove across a recording tape 6| which is progressively advanced yby -a clockwork or electrical timing mechanism. The instrument thus yields a 'trace showing the variation -in the potential which is applied thereto over any desired period t of time. By regulation of the sensitivity and dampening of the galvanometer, the instrument may be operated to yield an integrated reading.

In a circuit as illustrated in Figure 11, utilizing the resistance values noted above, and a -direct current plate supply voltage of -about 75 volts, the cathode tap |53 can be conveniently adjusted to give full scale deflection (100 scale divisions) of the instrument |51 at a potential of about -.20 volt `when the plate and grid of the tube I 41 are snorted, 4i. e. when the resistance across the test electrodes, the resistance Rx, is zero. When the resistance Rx increases to A1000 megohm's, the voltage applied to the galvanometer actuating element of the instrument |51 will drop to about .0S-volt with corresponding movement of the indicator pen |51 to about 30 scale divisions.

The voltage developed across the cathode resistor |5| may .also be used to control a powerdriven instrument of the general type illustrated -schematically in Figure 8. In general, a .poweractuated instrument is lalmost required with the variable shunt-resistance circuit of .Figure 8, due to relatively low output of that circuit under some operating conditions, but, las noted above, the increased output of the electronic tube circuit illustrated in Figure l1 makes possible the use of direct reading instruments -as well. Whether or not a circular or linear chart is used for recording is, of course, an optional consideratio'n.

The electronic circuit of Figure 1l has a further very important advantage in that it makes possiblegthe continuous indication of variations in moisture content across a moving web bythe use of a cathode ray oscilloscope. The resistance type mechanism is not adapted for use with instruments of this character, due to the fact that there is a substantial time lag in the operation of the mechanism which practically precludes cathode ray operation. The variation in the cathode current in the electronic tube apparatus is subject to no such limitations, however, and to obtain continuous indications of Vmoisture content, it becomes necessary merely to apply a potential obtained from the cathode resistor |5| to the vertical deilection plates of a cathode ray oscilloscope, as illustrated at |50, and to provide a suitable sweep voltage to the horizontal deflection plates in synchronism with the scanning or other sensing means used in conjunction with the apparatus. A suitable circuit for generating such a sweep voltage is shown in Figure 11, and as there illustrated, this circuit consists of a source |63 of direct current potential, which should have a magnitude of `from 'Sto 10 times the voltage required for complete horizontal deiiection of the cathode ray beam, 'and a series connected resistor |65 and condenser |61, as shown. The time constants of the R-C circuit should be such that 'the condenser Will charge to Within from 1/3 to 6 of the battery voltage in the time required for the scanning roll to make 'one 'revolution. Under these conditions the voltage rise across the condenser is sufficiently linear for practical purposes. In an actual embodiment of the apparatus, using a A DuMont oscilloscope wherein an applied voltage of -about 1.0 volt applied to the horizontal -amplier was required to produce a 4 inch horizontal deflection of the cathode ray beam and wherein the scanning roll turned at a rate` of 200 R. P. M., zthe voltage of the battery |63 equalled 22'1/2 volts, the resistance |65 had a value of 20 lmegohms, and the capacitance |61 was 1/2 microfarad. With a sweep voltage generator, as above described, itbecomes necessary merely to provide a condenser discharge switch |69 which is operable to short circuit the condenser |61 for an instant during each revolution of the scanning Aroll -|4|.

It will usually -be found necessary to amplify the voltage whichis applied to the vertical deiiection plates of the oscilloscope. Standard oscilloscopes utilizing 5 inch cathode ray tubes, -for example, are usually 'designed to -give a vertical deection of about one inch for applied voltages of the order of from 20 to 35 volts. The voltage obtainable across the cathode resistor |5| in the circuit of Figure 11 is normally not much `more-than about 60 volts, and accordingly, movement of the oscilloscope beam would be seriously'limi-ted 'wi-thout ampliiication. The built-in'amplier forming a part of the usual cathode ray oscilloscope will, however, usually provide ladequate amplication for this purpose.

.During operation of the system illustrated in Figure 1l, it will be 'evident that there :is available,

not only an integrated recording of the variation in moisture content cros'swi'se yor the paper web'. but also there is 'available a continuous visual 'indication showing the exact instantaneous variation in moisture content -across th'e web of paper as it is being manufactured or processed. This latter is a most important 'and most valuable 'feature of the invention, and is 'something which has heretofore been unavailable 'in the papermaking art. In actual tests o'f the 'equipment on a papermaking machine, the use of this continuous, crosswise indication o'f moisture content has made it possible for the machine operator to detect immediately the conditions 'resulting in formation of excess moisture content streaks, which sh'ow up on Ithe iin'i'she'd'paper, and't'o correct and 'overcome this diiiic'ulty with a minimum of delay. Important savings accompanied by increased paper quality thereby result.

The scanning or sensing roll 'is 'a n'ost 'important part of the invention. It will be understood, however, that both the novel resistance type ohmmeter indicating and recording system and the novel electronic indicating and recording system of the invention can be used in conjunction with sensing means 'of other types. For example, as previously described, the vsensing roll might comprise a series of insulated 'discs which are individually connected to a commutator 'and a brush contact can be employed to contact successively each'o'f these contact discs with result ant progressive sensing a'c'r'o's's 'the surface of 'the 13 web. Other arrangements will suggest themselves to those skilled in the art.

Also, the novel indicating and recording apparatus disclosed in the foregoing need not be utilized in conjunction with a sensing means operable to determine continuously the variation in moisture content across the face of the web. A single, narrow contact may be disposed in cooperative relation with a dried or other roll, and the resistance of this particular section of the web may be al1 that is measured. However, the circuit arrangements and structural combinations described above can be used to great advantage to provide linear, continuous indications of the variation in moisture contentl across the width of a moving web and to provide linear recordings of such variation. It is anticipated that the invention, in at least certain of its aspects, may nd application in other fields, for example, the textile and printing industries, Where continuous indications, based upon resistance values subject to non-linear variation, may be encountered.

The features of the invention believed to be new are expressly set forth in the appended claims.

We claim:

l. In apparatus which is operable to provide a continuous indication of variations in resistance across the width of a moving web or sheet; electrode means which moves progressively across the web or sheet under test in repetitive, cyclic manner during the use of said apparatus, while in contact with a segment of said web or sheet; resistance responsive means connected to said electrode means and operable to provide a voltage which varies with variation in the resistance of the segment of the web or sheet which is contacted by said electrode means at any particular instant during the use of said apparatus; a cathode ray oscilloscope having one pair of deflection plates connected to be energized in response to said voltage, and a second pair of deflection plates disposed at right angles to said rst mentioned pair; and a sweep voltage generator, which operates in synchronism with the repetitive cycle or" said electrode means, connected to said second pair of deection plates.

2. In apparatus which is operable to provide a continuous'v indication of variations in resistance across the width of a moving web of paper; electrode mee-ns which moves progressively across the web under test in repetitive, cyclic manner during use of said apparatus, While in contact with a segment of said web; a resistance responsive circuit which includes a source of potential, a thermionic tube unit having a plate connected to one side of said source of potential, a cathode connected to the other side of said source of potential through a cathode resistor, and a grid connected to said cathode resistor through a grid resistance, the plate and grid of said tube being connected to said electrode means, and said resistance responsive circuit being operable to produce a voltage across said cathode resistor which varies in response to variations in the resistance of the segment of the web between said electrodes at any particular instant during the use of said apparatus; a cathode ray oscilloscope having one pair of deflection plates connected to be energized in response to the voltages produced across said cathode resistance and a second pair of deflection plates disposed at right angles to said rst mentioned pair; and a sweep voltage generator, which operates in synchronism with the repetitive cycle of said electrode means, con- 14 nected to said second pair of deiiection plates.

3. In apparatus which is operable to provide a continuous indication of variations in resistance across the width of a moving web of paper; electrode means which moves progressively across the web under test in repetitive cyclic manner during'the use'of said apparatus, to contact successive segmental areas across said web width; said electrode means comprising a conducting surface over which the web may be moved and a rotatable member supported adjacent said conducting surface; the web under test passing between said conducting surface and said rotatable member, and said rotatable member having an electrode in the surface thereof; resistance re sponsive means connected to said electrode means, said resistance responsive means being operable to provide a voltage which varies substantially linearly in response to logarithmic variation in the resistance of the segment of the paper web which is between said conducting surface and said electrode at any particular instant during the use of said apparatus; a cathode ray oscilloscope,having one pair of deflection plates connected to be energized in response to said voltage, and a second pair of deflection plates disposed at right angles to said rst mentioned pair; and a sweep voltage generator, which operates in synchronism with the repetitive cycle of said electrode means, 'connected to said second pair of deection electrodes, whereby a continuous indication of the variation in moisture content across the Width of said web is obtained on the screen of said cathode ray oscilloscope.

4. In apparatus particularly adapted for determining variations in moisture content across a moving web of paper; a pair of electrodes, one of said electrodes comprising a roll having a conducting surface, and the other of said electrodes comprising a roll having an insulatingv surface and a narrow, ribbon-like, spirally shaped v contact supported in said insulating surface; said electrode contact making one complete turn about the axis of said roll; said rolls being supported adjacent each other to provide a nip and the web of paper under test being passed through the nip formed between said rolls whereby the said electrodes contact a ,small segment of paper, which segment moves progressively across the web of paper as said web moves through said rolls.

5. In apparatus particularly adapted for determining variations in moisture constant across a moving web of paper; a pair of electrodes, one of said electrodes comprising a roll having a conducting surface, and the other of said electrodes comprising a roll having an insulating surface and a narrow, ribbon-like contact supported in and extending spirally around said insulating surface; said rolls being supported adjacent each other to provide a nip and the web of paper under test being passed through the nip formed between said rolls whereby the said electrodes contact a small segment of paper, which segment moves across the web of paper as the web moves through said rolls.

6. In an apparatus for determining variations in resistance across a moving web or sheet; a pair of electrodes, one of which comprises a roll having a conducting surface over which the web or sheet under test may be moved, and the other of which comprises a rotatable member supported adjacent said conducting surface; said rotatable member comprising a roll having an insulating surface and at least one spirally shaped contact supported .in-said 'insulating fsurface, f the web or sheetlunder test passingth-rough:the-nip formed between vsaid rolls whereby `said :electr0des'contact a small segment of web, which segment moves acrossthe web in-a cyclic, repetitive manner as the web :moves :through said rolls, and means :for measuring the resistance connected to said electrodes whereby the'resistance `over-a small, Asegmental 'area at diierent points'across the width of said web-may be independently and continuously measured in a cyclic, repetitive manner.

7. -In vapparatus which isoperable to provide a continuous:indication of variations in--resistanceaeross thewidthiof'a-moving web or sheet; electrode means which: moves progressively-across vthe web or sheet under test in repetitive, cyclic manner during the use of said apparatus, while in contact with a segmentof said web or sheet; resistance responsive means connected to said electrode means and operable to provide a voltage which varies with variation in the resistance of Athe segment of the web or sheet which is .contacted by'said electroderneans at-any particular instant during the use Iof said apparatus; and an .indicating'means connected in voltage -responsive relationship with said 'resistance responsive means. said indicating means operatingin syn- 'chronismwith the repetitive cycle of 'said electrode .means and providing both a continuous indication of the segment of the web which -is contacted by said electrode means and of the resistance .of said contacted web segment.

8. In apparatus which is operable to provide -a continuous indication of variations in resistance across the width-.of a moving web of paper; electrode means which moves` progressively across 4the web under test in repetitive cyclic manner during the use of said apparatus to contact successive segmental areas across said -web width. f

said 'electrode means comprising a Aconducting surface over which the web vmay be :moved-and -a .rotatable member supported adjacent said conducting surface; the Web under test passing between said-conducting surface and fsaid rotatable member, and said rotatable member having an 'electrode in the surface .thereof resistance responsivemeans connected-to said electrode-means, Ysaid resistance responsivemeans being operable to provide a voltage which varies with variation in the resistance of the segment of the paper web which is between said vconducting surface and Ysaid electrode at .any particular instant `during the use of said apparatus; :and an indicating Jmeans, connected n voltage responsive relationship with said 'resistance .responsive means, said indicating means operating in synchronism with the repetitive cycle-of Y.said electrode means so -as to give a continuous indicationof both -theipositionof .said .electrode-on the web and the resistance of the 4web underneath said electrode.

9. In apparatus which is. operable to provide a continuous indication of variations in resistance across the -Width of a moving web of paper; electrodermeans which moves progressively across the web under test invrepetitive cyclic manner during the use of=said apparatus to contact successive segmental areas across said web width, saidelectrode -means comprising a conducting surface over which the web may be moved and a rotatable member .supported adjacent said conducting-surface; the .web under testpassing between said conducting surfaces and said rotatable member,and said rotatable member having an electrode in the .surface thereof; resistance responsive means `connected to saidl electrode means, said resistanceresponsive means being operable to providea voltage which varies substantially linearly in response to .logarithmic variation in vthe resistance of .the segment of thepaper web which .is between said conducting surface and said electrode at any particular instant during the use of said apparatus; vand an indicating means, connected in voltage responsive relationship with said resistance responsive means, said `indicating means operating in synchronism with therepetitive cycle of saidelectrode means so as 4to-give-acontinuous indication of both the positionof said electrode on the web and the resist- .ance of the web underneath said electrode.

LOWELL W. ZABEL. vltOBERT W. SCHMIDT.

RALPH H. CASTON.E.-

References Cited in the ile of this patent UNITED rSTATES PATENTS Number Date I 'Name 1,589,450 'Wilson let al June 22, 1926 2,133,725 "Sperry etal Oct. '18, 1938 2,220,489 Lowk'rantz Nov. 5, 1940 12,227,109 v'Shanlt'w'eiler Dec. 31, 1940 2,263,017 Sparrow Nov. 18, 1941 2,270,732 Jones Jan. 20, 1942 2,272,239 Delmhorst Feb. 10, 1942 2,371,636 4McConnell Mar. 20, 1945 '-2510,691 Gilbert June 6, 1950 :2,519,367 Gunn etal. Aug. 22, 1950 "25,579,316 Hall et al. Dec. 18, 1951 FOREIGN PATENTS Number ACountry Date v"11;410 Norway June 2, 1925 436,923 Great Britain Oct. 21, 1935 

